González served on the San Antonio City Council from 1953 to 1956, when he was elected to the Texas Senate, having defeated the Republican candidate, Jesse Oppenheimer. In 1960, he defeated another Republican, Ike Simpson Kampmann, Jr. (1918-2006).[6] He remained in the Senate until 1961 and set the filibuster record in the chamber at the time[7] by speaking for twenty-two straight hours against a set of bills on segregation. Most of the bills were abandoned (eight out of ten). He ran for governor in 1958, finishing second in the Democratic primary (the real contest for governor in what was then a solidly Democratic state) to Price Daniel. In January 1961, González ran in the special election for Lyndon Johnson's Senate seat, finishing sixth. However, in September, 20th District Rep. Paul J. Kilday was appointed to the Court of Military Appeals. González ran in the special election for the San Antonio-based district in November and defeated a strong Republican candidate, John Goode.[6] However, Gonzalez would never face another contest nearly that close. He was unopposed for a full term in 1962 and was reelected seventeen times. He never faced truly serious or well-funded opposition, having been unopposed in 1970, 1974, 1976, 1978, 1982, and 1984. In fact, the 20th was (and still is) so heavily Democratic that González faced Republican opposition only five times and handily won each time.

González became known for his liberal views. In 1963, Republican congressman Ed Foreman called González a "communist" and a "pinko" and González confronted him. González was referred to as a "communist" in 1986 by a man at Earl Abel's restaurant, a popular San Antonio eatery. The 70-year-old representative responded by punching him in the face. González was acquitted of assault for this incident.

According to Gretchen Morgenson's book on the 2008 financial meltdown, "Reckless Endangerment," while head of the House Banking Committee, Gonzalez invited the organization ACORN "to help legislators define the goals when they were devising the new legislation covering Fannie and Freddie."

On October 24, 2006, it was announced that González's personal notes, correspondence and mementos would become part of the Congressional History Collection at the University of Texas at Austin's Center for American History.